<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        // 需求：让用户输入年份，判断这一年是闰年还是平年并弹出对应的警示框
        let year = +prompt('请输入年份')
        if (year % 4 === 0 && year % 100 != 0 || year % 400 === 0) {
            alert(`${year}年是闰年`)
        } else {
            alert(`${year}年是平年`)
        }
    </script>
</body>
</html>